It is well-known today that both commercial and domestic activities produce an enormous amount of solid waste. Almost all of this waste is deposited into municipal landfills causing existing landfills to quickly fill to their capacity. Therefore, landfill space is significantly limited making it a valuable commodity. It is, therefore, necessary to efficiently utilize presently existing landfill space to its maximum landfill capacity. Developing new landfill sites or expanding existing ones could help alleviate the problem of dwindling landfill space. However, obtaining the necessary approvals for construction of new landfills on virgin land is extremely difficult. Therefore, this problem is preferably solved by maximizing the amount of solid waste existing landfill sites can handle.
Conventional landfilling techniques generally include spreading each load of newly introduced municipal solid waste into about one to five-foot high layers and then compacting the spread solid waste. These steps of spreading and compacting are repeated for each additional load of newly introduced waste, with the newly introduced waste being placed and compacted either adjacent to or on top of previously spread and compacted waste. At the end of the day, a daily covering material is typically placed onto the newly introduced waste. The process is repeated each day until the landfill site is filled, at which time the site is capped and venting is provided to prevent build-up of decomposition gases.
One problem with conventional landfill techniques is that the waste density is not maximized; hence, not as much waste is capable of being introduced into the landfill site before it is closed. This certainly affects the profitability of the landfill, but it is also a poses a significant problem to individual communities given the difficulties encountered in opening new landfill sites. Thus, it would be desirable to maximize the use of existing landfill sites by enhancing the in-place density of waste introduced into landfill sites.
A second problem with most conventional landfill sites is the need to remove and/or treat leachate, which is the liquid seepage recovered from landfill sites. It is typically sent to an off-site wastewater treatment facility or treated on-site prior to release of treated effluent into the environment.
In order to try to minimize the production of landfill leachate, many federal and state regulations attempt to keep the waste dry through the installation of impermeable landfill caps once the final grades have been achieved. Current regulations require landfill operators to fund a post-closure reserve account to maintain the landfill for a period of at least 30 years after the landfill is closed. An inherent criticism of landfill closure projects is that the partially decomposed waste is entombed by a relative water tight cap such that this waste has the potential to slowly degrade and contaminate groundwater resources for decades or even centuries after the 30-year post-closure period is ended. Hence post-closure liability concerns are very real for conventional landfill designs.
While others have proposed systems and methods for enhancing compaction and reduction in leachate treatment or leachate disposal costs, the systems and methods employed typically involve either labor or equipment-intensive steps, such as shredding of the waste prior to landfilling or injecting air into the waste, in order to overcome some of the above-described problems. With the addition of labor or equipment-intensive steps, the expense of landfilling municipal solid waste will become increasingly more expensive. With the increased expense, the landfill operator may realize little, if any, of the cost savings achieved by any increase in compaction densities.
Thus, it would be desirable to achieve significant increases in waste compaction densities and eliminate or minimize leachate treatment or disposal costs, while enhancing the decomposition process of organic wastes, but without significantly increasing the expense of landfilling waste as compared to conventional landfill operations.
The present invention relates to an improved method of treating municipal solid waste which overcomes these and other deficiencies in the art.